Insulator



Oct. 30, 1934. A. o. AUSTIN 1,979,092

INSULATOR Original Filed May 17. 1930 INVENTOR. BY A? M IQ 4% A TTORNEY5 Patented Get. 30, 1934 twat @FFEQE isracez EINSULATQE Jersey @riginalapplication May 1'7, 1930, Serial No.

453,180. Divided-and her 13, 1934, Serial Britain July 23, I930 21Claims.

This invention relates to insulators subjected to mechanical stressesandhas for its object the provision of devices of this class which shallbe of improved construction and operation and which are adapted toaccommodate themselves to conditions of stress and temperature to whichthey are subjected.

The invention is exemplified by the combination and arrangement of partsshown in the accompanying drawing and described in the followingspecification, and it is more particularly pointed out in the appendedclaims.

In the drawing the figure is an elevation with parts in section showingone embodiment of the present invention.

This application is a division of application Serial No. 453,180, filedMay 17, 1930, which is in part a continuation of application Serial No.32,715, filed May 25, 1925.

In suspension insulators or insulators used in tension of the usual capand pin form, there is a tendency for the metallic parts to distortunder heavy load. In addition, the differential expansion between themetal and porcelain also tends to change the relation of stress both inthe metal and the dielectric. Under some conditions the distortion ofthe metal may permit the re-arrangement of stress in the dielectric suchthat the dielectric member will be cracked, destroying its electricalreliability. One of the chief difficulties, particularly on insulatorsof high mechanical strength, is the radial distortion of the cap.

The figure shows one method of correcting this defect. The dielectricmember 50 is cemented into a cap 60. A pin 58 is cemented in a recess inthe head of the dielectric member. When load is applied to the cap andpin 58 by their attaching means, there is a tendency to pull thedielectric head out of the cap 60. The resultant pressure tends toexpand the cap 60. This has a tendency to permit the dielectricmember'to deform and crack under the stress. In order to onset theexpansion of the cap 60, the dielectric member is given a wedge shapedhead. The tapered bearing surfaces 54, 55 and 56 will maintain pressureagainst the cement by slipping down as the cap expands from increasedtemperature or due to the load. These surfaces are preferably smooth andcoated with graphite or some material which will lubricate the surface.The remainder of the head is preferably relieved from any stress bydipping or otherwise applying a yielding coat ing. It is evident thatwhile the expansion of the cap may be compensated for, it is alsoevident this application Septem- No. 743,881. In Great that the cap canset up a very heavy pressure tending to pinch the head off under lowtemperature conditions, particularly where the load or tension on theinsulator is slight. In order to relieve this maximum stress which tendsto shear off the head, two methods may be used. The radial stress set upby the cap may be reduced by providing it with slots suitably spaced.This tends to taper 01f the radial pressure and minimize the danger ofshearing, particularly under low temperatures. This construction hasdistinct advantages over a construction where the cement is allowed toslip in the cap. In the latter case the tangential forces in the cementtend to make it diificult to control the pressure between the dielectricand the cement. Where the dielectric, however, has a tapered head, thecement being comparatively weak in tension can always expand and permitadjustment of the head for a distortion in the cap.

A tapered surface to permit slipping for maintaining the radial pressurein the cement'may be applied also to the inner surface of thedielectric. The tapered surfaces 51, 52 and 53 are preferably coatedwith graphite or graphite and'wax or oil. When a heavy load is appliedto the attachments 58 and 60, the resultant forceon the head of thedielectric member 50 tend to cause it to deform. The radial distortiontends to weaken .the cement and permit shearing at a lower load. In thisparticular case this is compensated for by the cement sliding on thetapered surfaces 51, 52, 53, 54, 55 and 56 so as to maintain properradial pressure, The grading of the stress may be materially improved bythe use of a pin 58 having resilient flanges which have been describedin my previous'Patent No. 1,489,689, dated April 8, 1924.

In insulators having large bearing surfaces, the reduction of thediameter of the head, due

to its tapered form, is very material where the stress is carried on asingle bearing surface extending for a considerable distance along theaxis of the insulator. This may be ofiset as shown in the drawing. Inthis case several tapered surfaces 54, 55 and 56 are provided on theoutside of the head of the dielectric 50. These surfaces are preferablycoated as previously explained and the head coated with a yieldingmaterial. The angularity of the tapered bearing surfaces 54, 55 and-56may be changed so that the stress may be tapered ofi' at the endsurfaces and the heaviest load placed on 55. This tends to reduce theshearing stress and permits of an increased load being placed on theinsulator without danger of lilo . angularity may be varied inaccordance to the I causing a stress which will crack the dielectric.The stress on the inner surface may be carried by a cement joint, theload being distributed by the use of a resilient pin and resilientsanded surface, as explained in my previous Patent No. 1,284,975, datedNovember 19, 1918. As heavy loads or tensionson the insulator usuallyoccur at low temperatures, there is a tendency for the cap to contractunder these conditions and compensate for deformation caused by thestresses Set up by the load. In this case, it may not be necessary toapply any compensation to the cap, particularly where the latter has aheavy cross section. The pin, however, has a tendency to contract andrelieve the stress as well as the cement, which usually has a lowerlinear coefficient of expansion for temperature changes. By providingthe inner surface of the dielectric with slipping surfaces 51, 52 and53, as shown in the drawing, it is possible to maintain the radial forceon the cement between the surface of the dielectric and the pin. Aspreviously explained, this surface is preferably coated with a thincoating of graphite, wax,ol of some combination in order to control thecoefficient of friction. Where slipping is desired, it is necessary touse some material on the surface, for if Portland cement isused, thereis likely to be a slight bond between the cement and surface in time sothat slipping will not take place except at excessive loads. The slopeof the bearing surfaces 51, 52 and 53 may be changed as to angle asshown in the drawing in order to control the stress. A material controlin the stress may also be effected by the use of a pin having resilientflanges or through the control of the effective cross-section in thepin.

It is evident that compensating surfaces may be applied to both theinner and the outer surfaces of the dielectric. This is shown in thedrawing. A dielectric member 50 is equipped with inner sloping surfaces51, 52 and 53 and .outer sloping surfaces 54, 55 and 56. The innersurfaces permit compensating for deformation or changes in the innerwall of the dielectric as well as in the cement 57 and pin 58. Ingeneral, however, by the use of a resilient pin, a grading of the stresson the inner surface may be effected by controlling the relativestiffness of the flanges on the pin at different points. The taperedslipping on the outside of 54, 55 and 56 tends to compensate for cap anddielectric deformation as well as the deformation of the cement 59between the dielectric 50 and the cap 60. The

conditions which it is desired to set up and may vary considerably fordifferent designs.

If the metal is allowed to slip, the cement may absorb a large part ofthe force due to the radial component set-up in the cement. In the casewhere the dielectric member slips, however, the cement being weak intension simply checks at different places and permits the properrelation between the parts, tending to develop a high ultimate for agiven area.

In the case of the inner tapered surface, the cement projects betweenthe flanges of the resilient pin, forming annular rings or galleries.These galleries may be given an appreciable defiection and form a partof the means for distributing the load. If these galleries are tofunction properly, it is important that the radial forces or pressure bemaintained. This is effected by placing the compensating surface on thedielectric, The resilient caps in accordance with my previous'Patent No.1,552,663, dated September 8,

1925, may be used to advantage in order to distribute the load properlyto make up for any unevenness on the coating of the surface or toprevent excessive stress due to contraction at low temperature.

I claim:

1. An insulator comprising a dielectric member, a fitting for saiddielectric member, said dielectric member having a plurality of smoothinclined bearing surfaces differing from one another in angularity andregistering with said fitting, and a lubricating coating disposed onsaid bearing surfaces to facilitate sliding thereof under the force ofthe load on said insulator.

2. An insulator comprising a dielectric member, a cap for saiddielectric member, cement interposed between said dielectric member andcap, said dielectric member having a plurality of bearingsurfacesinclined at different angles to exert a wedging action on the cement andto grade the stress transmitted between said cap and dielectric member,and a lubricating coating disposed on said bearing surfaces tofacilitate slipping between said dielectric member and cement, the

edge of said cap having a weakened portion to produce a gradient in thepressure exerted on said dielectric member at the edge of said cap.

3. In an insulator, a dielectric member having a plurality of taperedbearing surfaces, a second member cooperating with said surfaces, saidsurfaces differing in' angularity to grade the stress in said dielectricmember, a central surface having greater angularity than surfaces ateither side thereof.

4. An insulator comprising a dielectric member, a holding member securedto said dielectric member, said dielectric member having a plurality oftapered bearing surfaces cooperating with said holding member anddiffering in angularity to grade the stress in said dielectric member,the

angularity of said surfaces decreasing from a cen- 1 tral position.

5. An insulator comprising a dielectric member, a fitting for saiddielectric member, said dielectric member having a plurality of smoothinclined bearing surfaces differing from one another in angularity andregistering with said fitting, the angularity. of said bearing surfacesbeing greatest at a central position and decreasing in oppositedirections from said central position, and a lubricating coatingdisposed on said bearing surfaces to facilitate sliding thereof underthe force of the load on said insulator.

6. An insulator comprising a fitting, a dielectric member having aplurality of tapered bearing surfaces distributed along a face of saiddielectric member, said fitting having bearing surfaces cooperating withthe bearing surfaces of said dielectric member and arranged to slipunder the load on said insulator to compensate for deformation in theparts of said insulator, said surfaces differing from one another inangularity to control the distribution of stresses on said dielectricmember, the coefficient of friction between cooperating surfaces beinglow, enough to permit reverse slipping of said surfaces under forcenormal to the direction of the load.

7. An insulator comprising a dielectric member, a fitting for saiddielectric member, cement interposed between said fitting and dielectricmember and having inclined bearing surfaces, said dielectric memberhaving a plurality of smooth bearing surfaces in registration with thebearing surfaces of said cement, the bearing surfaces of said dielectricmember being inclined at different angles evaoea the influence of theload on said insulator and to grade the distribution of stresstransmitted between said fitting and dielectric member, the coefficientof friction between said registering hearing surfaces being low enoughto permit relative movement of said surfaces under force normal to theload on said surfaces.

3. An insulator comprising a non-conducting shell, 2, pin, said shellhaving a recess therein receiving'one end of said pin, which recess hasa strain receiving surface tapering inwardly towards the free end of thepin, cement filler within the recess and surrounding the pin to retainthe pin in position within the shell, said shell having an outer strainreceiving surfac'e tapering in the same direction as the strainreceiving surface of the recess, a cap embracing said outer strainreceiving surface and cement filler within the cap and surrounding saidouter strain receiving surface to retain the cap and shell in properrelationship, said strain receiving surfaces being unbonded with thefillers adjacent thereto 9. An insulator comprising a non-conductingshell, a pin, said shell having a recess therein receiving one end ofthe pin, which recess has a strain receiving surface tapering inwardlytowards the free end of the pin, cement filler within the recess andsurrounding the pin to retain the pin in position within the shell, saidshell having an outer strain receiving surface tapering in the samedirection as the strain receiving surface of the recess, a cap embracingsaid outer strain receiving surface, cement filler within the cap andsurrounding said outer strain receiving surface to retain the cap andshell in proper relationship, and yielding coatings separating thestrain receiving surfaces from the fillers adjacent thereto.

10. An insulator comprising a non-conducting porcelain shell, a pin,said shell having a recess therein receiving one end of said pin, whichrecess has a strain receiving surface tapering inwardly towards the freeend of the pin, cement filler within the recess and surrounding the pinto retain the pin in position within the shell, said shell having anouter strain receiving surface tapering in the same direction'as thestrain receiving surface of the recess, a cap embracing said outerstrain receiving surface, and cement filler within the cap andsurrounding said outer strain receiving surface to retain the cap andshell in proper relationship, the strain receiving surface of the recessbeing unbonded with the flller within said recess.

11. An insulator comprising a non-conducting porcelain shell, a pin,said shell having a recess therein receiving one end of said pin, whichrecess has a strain receiving surface tapering inwardly towards the freeend of the pin, cement filler within the recess and surrounding the pinto retain the pin in position within the shell, said shell having anouter strain receiving surface tapering in the same direction as thestrain receiving surface of the recess, a cap embracing said outerstrain receiving surface, a cement filler within the cap and surroundingsaid outer strain receiving surface to retain the cap and shell inproper relationship, said outer strain receiving surface being unbondedwith the filler within the cap.

12. An insulator comprising a non-conducting porcelain shell, a pin,said shell having a recess therein receiving one end of said pin, whichrecess has a strain receiving surface tapering inwardly towards the freeend ofthe pin, cement filler withi in the recess and surrounding thepinto retain the pin in position within the shell, said shell havingtherein receiving one end of said pin, the surface of said recess havingstrain receiving portions, cement filler within the recess andsurrounding the pin to-retain the pin in position within the shell, saidshell having an outer surface having strain receiving portions, a capembracing said outer surface, and cement filler within the cap andsurrounding said outer surface to retain the cap and shell in properrelationship, the strain receiving portions of the surface of the recessbeing unbonded with the filler within said recess.

14'. An insulator comprising a non-conducting porcelain shell, a pin,said shell having a recess therein receiving one end of said pin, thesurface of said recess having strain receiving portions, cement fillerwithin the recess and surrounding the pin to retain the pin in positionwithin the shell, said shell having an outer surface having strainreceiving portions, a cap embracing said outer surface, a cement fillerwithin the cap and surrounding said outer surface to retain the cap andshell in proper relationship, the strain receiving portions of the outersurface being u'nbonded with the filler within the cap.

15. An insulator comprising a non-conducting therein receiving one endof said pin, which recess has strain receiving portions taperinginwardly towardsthe free end of the pin, cement filler within the recessand surrounding the pin to retain the pin in position within the shell,said shell having outer strain receiving portions opposed to,andtapering in thessame direction as, the strain receiving portions of therecess, a cap embracing said outer strain receiving portions, and cementfiller within the cap and surrounding said outer strain receivingportions to retain the cap' and shell in proper relationship, saidstrain receiving portions being unbonded with the fillers adjacentthereto.

16. An insulator comprising a non-conducting porcelain shell, a pin,said shell having a recess therein receiving one end of the pin, whichrecess has a strain receiving surface tapering inwardly towards the freeend of the pin, cement filler face of the recess, a cap embracing saidouter strain receiving surface, cement filler within the cap andsurrounding said outer strain receiving surface to retain the cap andshell in proper relationship, and a resilient coating separating thestrain receiving surface ofthe recess from the filler therein.

17. An insulator comprising a non-conducting porcelain shell, a pin,said shell having a recess therein receiving one end of the pin, whichrecess has a strain receiving surface tapering inwardly towards the freeend of the pin, cement filler within the recess and surrounding the pinto retain the pin in position within the shell, said shell having anouter strain receiving surface tapering in the same direction as thestrain receiving 5 surface of the recess, a cap embracing said outerstrain'receiving surface, cement filler within the cap and surroundingsaid outer strain receiving surface to retain the cap and shell inproper relationship, and a resilient coating separating the from thefiller towards the free end of the pin, cement filler within the recessand surrounding the pin to retain the pin in position within the shell,said shell having an outer strain receiving surface tapering in the samedirection as the strain receiving surface of the recess, a cap embracingsaid outer strain receiving surface, cement filler within the cap andsurrounding said outer strain receiving surface to retain the cap andshell in proper relationship, and resilient coatings separating thestrain receiving surfaces from the fillers adjacent thereto.

19. An insulator comprising a non-conducting porcelain shell, a pin,said shell having a recess therein receiving one end of said pin, thesurface of said recess having strain receiving portions, cement fillerwithin the recess and surrounding the pin to retain the pin in positionwithin the shell, said shell having an outer surface having strainreceiving portions, a cap embracing said outer surface, cement fillerwithin the cap and surrounding said outer surface to retain the capporcelain shell, a pin, said shell having a recess therein receiving oneend of said pin, the surface of said recess having strain receivingportions, cement filler within the recess and surrounding the pin toretain the pin in position within the shell, said'shell having an outersurface having strain receiving portions, a cap embracing said outersurface, cement filler within the cap and surrounding said outer surfaceto retain the cap and shell in proper relationship, and a resilientcoating separating the strain receivingportions of the outer surfacefrom the filler within the cap and rendering them unbonded with thefiller.

21. An insulator comprising a non-conducting porcelain shell, a pin,said shell having a recess therein receiving one end of said pin, thesurface of said recess having strain receiving portions, cement fillerwithin the recess and surrounding the pin to retain the pin in positionwithin the shell, said shell having an outer surface having strainreceiving portions, a cap embracing said outer surface, cement fillerwithin the cap and surrounding said outer surface to retain the cap andshell in proper relationship, and resilient coatings separating thestrain receiving portions of the surfaces from the fillers adjacentthereto and rendering them unbonded with the fillers.

ARTHUR O. AUSTIN.

